Volume displacement determines water added

Steps:

• Calculate paraffin mass: 100 cm³ × 0.8 g/cm³ = 80 g.
• Determine water volume: total 150 cm³ - initial 100 cm³ = 50 cm³.
• Calculate water mass: 50 cm³ × 1 g/cm³ = 50 g.
• Total mass: 80 g + 50 g = 130 g.

Why A is correct:

• Total mass equals sum of each liquid's mass (volume × density), as they are immiscible and layer separately.

Why the others are wrong:

• B: Assumes average density of 0.933 g/cm³ for total volume, ignoring separate layers.
• C: Incorrectly uses total volume with wrong average density (e.g., 150 × 1.11 g/cm³).
• D: Treats entire 150 cm³ as paraffin (150 × 1.167 g/cm³, misapplied).

Final answer: A